split and merge file into zip chunks

mergeZips.ps1

$destination = 'path\to\destination'
$inFS = [System.IO.File]::OpenWrite($destination)

Get-ChildItem -Filter temp* | ForEach-Object {
    $stream = $_.OpenRead()
    $zip    = [System.IO.Compression.ZipArchive]::new($stream, [System.IO.Compression.ZipArchiveMode]::Read)
    $entry  = $zip.GetEntry($_.Name)
    $zipFS  = $entry.Open()
    $zipFS.CopyTo($inFS)
    $zipFS, $zip, $stream | ForEach-Object Dispose
}

$inFS.Dispose()

splitFile.ps1

$inFile = Get-Item path\to\filetosplit
$inFS   = $inFile.OpenRead()
$buffer = [byte[]]::new(200mb)
$chunk  = 0

while($readBytes = $inFS.Read($buffer, 0, $buffer.Length)) {
    $name  = '{0}-part {1:D2}.{2}' -f $inFile.BaseName, $chunk, $inFile.Extension
    $file  = Join-Path $pwd.Path -ChildPath $name
    $outFS = [System.IO.File]::OpenWrite($file + $inFile.Extension)
    $zip   = [System.IO.Compression.ZipArchive]::new($outFS, [System.IO.Compression.ZipArchiveMode]::Create)
    $entry = $zip.CreateEntry($name + $inFile.Extension)
    $zipFS = $entry.Open()
    $zipFS.Write($buffer, 0, $readBytes)
    $chunk++
    $zipFS, $zip, $outFS | ForEach-Object Dispose
}

$inFS.Dispose()